This invention pertains to electrically powered intense illumination of short duration.
The re-usable flash-tube has been an important item in photography for a number of years. Typically, the brightness of the flash has been fixed, or adjustable in only coarse increments.
Relatively complicated devices have been developed for the exacting demands of professional photography, and circuits have been evolved to accomplish variations in design of the devices.
One design employs an unconventional type of flash-tube having closely spaced electrodes, between which a spark is struck to start the flash. Since the voltage required to produce the spark is many times the voltage that the charge-accumulating capacitor can withstand, a unilateral conductor is employed between the flash-tube and that capacitor. It is poled so that the high sparking voltage cannot be conducted to the capacitor.
Another design employs an electronic counter to successively connect charged capacitors to the flash-tube. The counter is stopped by an automatic, or equivalent, control that determines that enough light has been flashed to handle the photography at hand. Through a multiplexer, successive silicon-controlled-rectifiers are triggered to discharge the number of capacitors required for the given photography. This process is accomplished by external control; not by self control that depends upon the potentials involved.
Still another design employs plural capacitors, but the number of capacitors that will be charged and discharged is selected by a manually operated switch. This allows adjustment of the light flash only in relatively gross steps, rather than incrementally over a wide range.